|
|
Atomic Number: |
87 |
Melting Point: | 27 ºC | |
| Atomic Symbol: | Fr | Boiling Point: | 677 ºC | ||
| Atomic Weight: | 223 amu | Density: | 1870
kg/m 3 |
||
| Atomic Radius: |
270 pm |
Oxidation States: | 1 | ||
| Covalent Radius: | NA | Electron Configuration: | [Rn]7s1 | ||
| van der Waals Radius: |
NA |
State of Matter: | solid |
(France) Discovered in 1939 by Mlle. Marguerite Perey of the Curie Institute, Paris.
Francium, the heaviest known member of the alkali metals series. It has the highest equivalent weight of any element, and is the most unstable of the first 101 elements of the periodic system. No weighable quantity of the element has been prepared or isolated. The chemical properties of francium most resemble cesium.
Francium occurs as a result of an alpha disintegration of actinium. It can also be made artificially by bombarding thorium with protons. While it occurs naturally in uranium minerals, there is probably less than an ounce of francium at any time in the total crust of the earth.
Due to its scarcity and short half life, there are not many uses for francium other than scientific research.
Thirty-three isotopes of francium are recognized. The longest lived 223Fr (Ac, K), a daughter of 227Ac, has a half-life of 22 min. This is the only isotope of francium occurring in nature. Because all known isotopes of francium are highly unstable, knowledge of the chemical properties of this element comes from radiochemical techniques.
Since francium has not been able to be isolated or prepared, it does not present any hazards. However, as part of the alkali group, similar hazards may apply.
